import java.util.UUID;

public class Demo {

    public static void main(String[] args) {
        String uuid = UUID.randomUUID().toString();
        //910827c7-f089-4ff0-889b-5c9b307e4d66
        System.out.println(uuid);
        //041838957bbe4759847db881c7f21adc
        System.out.println(uuid.replace("-", ""));

        String name = "a.png";
        System.out.println(name.substring(name.lastIndexOf(".") + 1));
    }
}
